我有一个函数应该根据特征索引对2D String数组进行排序。这是我的4个元素的2D数组（4 x 10）。
String[][] testArr = {
{"192.168.1.101-67.212.184.66-2156-80-6","192.168.1.101","2156","67.212.184.66","80","6","13/06/2010 06:01:11","2328040","2","0"}
,{"192.168.1.101-67.212.184.66-2159-80-6","192.168.1.101","2159","67.212.184.66","80","6","13/06/2010 06:01:11","2328006","2","0"}
,{"192.168.2.106-192.168.2.113-3709-139-6","192.168.2.106","3709","192.168.2.113","139","6","13/06/2010 06:01:16","7917","10","9"}
,{"192.168.5.122-64.12.90.98-59707-25-6","192.168.5.122","59707","64.12.90.98","25","6","13/06/2010 06:01:25","113992","6","3"}
};
我想根据它们的第7个索引对这些元素进行排序，分别是（2328040,2328006,7917,113992）。这是我为它写的函数：
// ************MERGE SORT***************************
public static void mergeSort(String[][] arr,int featureIndex){
mergeSort(arr,new String [arr.length][10],0,arr.length-1,featureIndex);
}
// MERGE SORT HELPER FUNCTION
public static void mergeSort(String[][] arr,String [][] temp,int leftStart,int rightEnd,int featureIndex){
if(leftStart >= rightEnd){
return;
}
int mid = (leftStart + rightEnd)/2;
mergeSort(arr,temp,leftStart, mid,featureIndex);
mergeSort(arr,temp,mid + 1, rightEnd,featureIndex);
mergeHalves(arr,temp,leftStart,rightEnd,featureIndex);
}
// Merge 2 Halves
public static void mergeHalves(String[][] arr,String[][] temp,int leftStart,int rightEnd,int featureIndex){
int leftEnd = (rightEnd + leftStart)/2;
int rightStart = leftEnd + 1;
int size = rightEnd - leftStart + 1;
int left = leftStart;
int right = rightStart;
int index = leftStart;
while(left <= leftEnd && right <= rightEnd){
if(Double.parseDouble(arr[left][featureIndex]) <= Double.parseDouble(arr[right][featureIndex])){
temp[index][featureIndex] = arr[left][featureIndex];
left++;
}else{
temp[index][featureIndex] = arr[right][featureIndex];
right++;
}
index++;
}
// Copy the arrays
System.arraycopy(arr, left, temp, index, leftEnd - left + 1);
System.arraycopy(arr, right, temp, index, rightEnd - right + 1);
System.arraycopy(temp, leftStart, arr, leftStart, size);
}
当我运行程序时，它会分别为每个元素打印出7917 7917 7917 113992.
答案 0 :(得分：2)
这是一个很好的问题，因为它带来了使用不同类型的列对表进行排序的复杂问题。 Java的更高版本实现了您可以使用的新排序工具。这是我使用JDK 1.8（Java 8）解决问题的方法。它只打印字段0,1,7，尽管您可以轻松添加其余字段。
头等档案：
package intquestions;
import java.util.ArrayList;
import java.util.Collections;
import static java.lang.System.out;
import intquestions.StaffComparator;
public class SortDataList {
public static void main(String[] args) {
runit(); }
public static void runit() {
Object[] list1 = {"192.168.1.101-67.212.184.66-2156-80-6","192.168.1.101","2156","67.212.184.66","80","6","13/06/2010 06:01:11",2328040,"2","0" };
Object[] list2 = {"192.168.1.101-67.212.184.66-2159-80-6","192.168.1.101","2159","67.212.184.66","80","6","13/06/2010 06:01:11",2328006,"2","0"};
Object[] list3 = {"192.168.2.106-192.168.2.113-3709-139-6","192.168.2.106","3709","192.168.2.113","139","6","13/06/2010 06:01:16",7917,"10","9"};
Object[] list4 = {"192.168.5.122-64.12.90.98-59707-25-6","192.168.5.122","59707","64.12.90.98","25","6","13/06/2010 06:01:25",113992,"6","3"};
ArrayList<DataList> mList=new java.util.ArrayList<DataList>();
mList.add(new DataList(list1));
mList.add(new DataList(list2));
mList.add(new DataList(list3));
mList.add(new DataList(list4));
String sep = " | " ;
out.println("BEFORE SORTING - ONLY PRINTING FIELDS 1,2,8 (0,1,7) ---------------------- : " );
out.println(mList.get(0).s.toString() +sep+ mList.get(0).f.toString() +sep+ mList.get(0).eighth.toString());
out.println(mList.get(1).s.toString() +sep+ mList.get(1).f.toString() +sep+ mList.get(1).eighth.toString());
out.println(mList.get(2).s.toString() +sep+ mList.get(2).f.toString() +sep+ mList.get(2).eighth.toString());
out.println(mList.get(3).s.toString() +sep+ mList.get(3).f.toString() +sep+ mList.get(3).eighth.toString());
StaffComparator myComparator = new StaffComparator();
try { Collections.sort(mList, myComparator);
} catch (Exception e) { out.println(e); }
out.println("\nDONE SORTING - ONLY PRINTING FIELDS 1,2,8 (0,1,7) ----------------------- : " );
out.println(mList.get(0).s.toString() +sep+ mList.get(0).f.toString() +sep+ mList.get(0).eighth.toString());
out.println(mList.get(1).s.toString() +sep+ mList.get(1).f.toString() +sep+ mList.get(1).eighth.toString());
out.println(mList.get(2).s.toString() +sep+ mList.get(2).f.toString() +sep+ mList.get(2).eighth.toString());
out.println(mList.get(3).s.toString() +sep+ mList.get(3).f.toString() +sep+ mList.get(3).eighth.toString());
}
}
class DataList extends DataListAbstract {
public DataList(Object[] myObj) {
super(myObj); }
public Integer getEighth(DataList locVarDataList) {
return locVarDataList.eighth; }
@Override
public int compareTo(DataListAbstract o) {
return 0; }
}
abstract class DataListAbstract implements Comparable<DataListAbstract> {
String f; // first
String s; //second
Integer eighth;
DataListAbstract(Object[] myo) {
this.eighth = (Integer)myo[7];
this.f = (String)myo[0];
this.s = (String)myo[1];
}
}
第二课：
package intquestions;
import java.util.Comparator;
public class StaffComparator implements Comparator<DataList> {
public int compare(DataList c1, DataList c2) {
Integer firstInt = c1.getEighth(c1);
Integer secondInt = c2.getEighth(c2);
return firstInt.compareTo(secondInt);
}
}
输出：
BEFORE SORTING - ONLY PRINTING FIELDS 1,2,8 (0,1,7) ---------------------- :
192.168.1.101 | 192.168.1.101-67.212.184.66-2156-80-6 | 2328040
192.168.1.101 | 192.168.1.101-67.212.184.66-2159-80-6 | 2328006
192.168.2.106 | 192.168.2.106-192.168.2.113-3709-139-6 | 7917
192.168.5.122 | 192.168.5.122-64.12.90.98-59707-25-6 | 113992
DONE SORTING - ONLY PRINTING FIELDS 1,2,8 (0,1,7) ----------------------- :
192.168.2.106 | 192.168.2.106-192.168.2.113-3709-139-6 | 7917
192.168.5.122 | 192.168.5.122-64.12.90.98-59707-25-6 | 113992
192.168.1.101 | 192.168.1.101-67.212.184.66-2159-80-6 | 2328006
192.168.1.101 | 192.168.1.101-67.212.184.66-2156-80-6 | 2328040